Low Profile Instrument Immobilizer

ABSTRACT

This document discusses, among other things, examples of a low profile instrument immobilizer and means for positioning the same. In one example, the low profile instrument immobilizer grasps, secures, and immobilizes an electrode or other instrument that extends through a burr hole in a skull to a target location in a patient&#39;s brain.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 11/005,907filed Dec. 6, 2004, which is a continuation-in-part of PCT/US2003/028966filed Sep. 17, 2003 and published in English on Apr. 1, 2004 as WO2004/026161 A2, which claimed priority to U.S. Provisional ApplicationNo. 60/411,309 filed Sep. 17, 2002, which applications and publicationare incorporated herein by reference.

FIELD OF THE INVENTION

This document relates generally to instrument immobilizers, and morespecifically, but not by way of limitation, to a low profile instrumentimmobilizer.

BACKGROUND

Neurosurgery sometimes involves inserting an electrode (for recordingbrain signals or providing stimulating pulses) or other instrument (forexample, a catheter for fluid aspiration or drug infusion) through aburr hole or other entry portal into a subject's brain toward a targetregion of the brain. In certain applications, there is a need to securethe electrode or other instrument in place after it has been introduced,potentially for an extended period of time. Moreover, in certainapplications, other equipment (such as a trajectory guide and anyassociated equipment) is mounted to the patient's skull about the burrhole.

For these and other reasons, which will become apparent upon reading thefollowing detailed description and viewing the drawings that form a partthereof, the present inventors have recognized an unmet need for lowprofile instrument immobilizer devices, tools, and methods that reduceor avoid patient discomfort and also better retain instruments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsdescribe substantially similar components throughout the several views.Like numerals having different letter suffixes represent differentinstances of substantially similar components. The drawings illustrategenerally, by way of example, but not by way of limitation, variousembodiments discussed in the present document.

FIG. 1 is a top view illustrating generally, by way of example, but notby way of limitation, portions of a first instrument immobilizer.

FIG. 2 is a top view illustrating generally an example of portions ofthe first instrument immobilizer after cover pieces have been partiallyinserted into respective slots in opposing sides of a hoop.

FIG. 3 is a perspective view illustrating generally an example ofportions of the first instrument immobilizer after the cover pieces havebeen partially inserted into the respective slots of the hoop.

FIG. 4 is a side view illustrating generally an example of portions ofthe first instrument immobilizer after the cover pieces have been almostfully inserted into the respective slots of the hoop.

FIG. 5 is a top view illustrating generally an example of portions ofthe first instrument immobilizer after the cover pieces have been fullyinserted into the respective slots of the hoop.

FIG. 6 is a perspective view illustrating generally, by way of example,but not by way of limitation, portions of a second instrumentimmobilizer.

FIG. 7 is a side view of the second instrument immobilizer with a latchpiece in an open position.

FIG. 8 is a perspective view of the second instrument immobilizer withthe latch piece in a closed position.

FIG. 9 is a side view of the second instrument immobilizer with thelatch piece in a closed position.

FIG. 10 is a top view of a third instrument immobilizer.

FIG. 11 is a top view of the third instrument immobilizer with a claspin a closed position.

FIG. 12 is a perspective view of the third instrument immobilizer withthe clasp in its closed position.

FIG. 13 is a side view of the third instrument immobilizer with theclasp in its open position.

FIG. 14 is a side view of the third instrument immobilizer with theclasp in its closed position.

FIG. 15 is a perspective view of a fourth instrument immobilizer withbase pieces in an open position.

FIG. 16 is a top view of the fourth instrument immobilizer with basepieces in a closed position, grasping and immobilizing a laterally bentelectrode.

FIG. 17 is a top view of a fifth instrument immobilizer.

FIG. 18 is a top view illustrating the fifth instrument immobilizerwhere the first retaining member and second retaining member immobilizean instrument.

FIG. 19 is a top view of a sixth instrument immobilizer.

FIG. 20 is a top view illustrating the sixth instrument immobilizerwhere the socket slot and socket immobilize an instrument.

FIG. 21 is a perspective view of another example of the lid for thesixth instrument immobilizer having multiple slots and correspondingsockets.

FIG. 22 is a top view illustrating generally the first instrumentimmobilizer where the cover pieces immobilize an instrument.

FIG. 23 is a perspective view of the second instrument immobilizer withthe latch piece in the closed position where the latch piece immobilizesan instrument.

FIG. 24 is a perspective view of the third instrument immobilizer withthe clasp in the closed position where the clasp immobilizes aninstrument.

FIG. 25 is a perspective view of an apparatus for positioning aninstrument immobilizer within a burr hole.

FIG. 26 is a top view of an instrument immobilizer coupled to anapparatus for positioning an instrument immobilizer.

FIG. 27 is an exploded view of an apparatus for positioning aninstrument immobilizer, an instrument immobilizer, a cap and a burr holehaving including a countersink.

FIG. 28 is a perspective view of another example of an apparatus forpositioning an instrument immobilizer within a burr hole.

FIG. 29 is a perspective view of yet another example of an apparatus forpositioning an instrument immobilizer within a burr hole.

FIG. 30 is an exploded view of still another example of an apparatus forpositioning an instrument immobilizer within a burr hole.

FIG. 31A is an exploded view of an additional example of an apparatusfor positioning an instrument immobilizer within a burr hole.

FIG. 31B is an exploded view of a further example of an apparatus forpositioning an instrument immobilizer within a burr hole.

FIG. 31C is an exploded view of a supplementary example of an apparatusfor positioning an instrument immobilizer within a burr hole.

FIG. 32 is a block diagram illustrating generally, by way of example,and not by way of limitation, a first method to immobilize aninstrument.

FIG. 33 is a block diagram illustrating generally, by way of example,and not by way of limitation, a second method to immobilize aninstrument.

FIG. 34 is a block diagram illustrating generally, by way of example,and not by way of limitation, a third method to immobilize aninstrument.

FIG. 35 is a block diagram illustrating generally, by way of example,and not by way of limitation, a fourth method to immobilize aninstrument.

FIG. 36 is a block diagram illustrating generally, by way of example,and not by way of limitation, a fifth method to immobilize aninstrument.

FIG. 37 is a block diagram illustrating generally, by way of example,and not by way of limitation, a sixth method to immobilize aninstrument.

FIG. 38 is a block diagram illustrating generally, by way of example,and not by way of limitation, a first method to position an instrumentimmobilizer.

FIG. 39 is a side view of one example of a countersinking drill bit forcutting a countersink into a burr hole.

FIG. 40 is a block diagram illustrating generally, by way of example,and not by way of limitation, a second method to position an instrumentimmobilizer.

FIG. 41 is a block diagram illustrating generally, by way of example,and not by way of limitation, a third method to position an instrumentimmobilizer.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. Furthermore, allpublications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this documents and those documents so incorporated byreference, the usage in the incorporated reference(s) should beconsidered supplementary to that of this document; for irreconcilableinconsistencies, the usage in this document controls.

FIGS. 1-5 and 22 illustrate various views of a first embodiment of alow-profile instrument immobilizer for securing a flexible recording orstimulating electrode or the like, or other instrument (such as acatheter for fluid aspiration or drug, cell, or substance infusion)after it has been introduced through a burr hole or other entry portalto a desired target location in the brain.

FIG. 1 is a top view illustrating generally, by way of example, but notby way of limitation, portions of instrument immobilizer 100. In thisexample, instrument immobilizer 100 includes a hoop-like base 102 (alsoreferred to herein as a “hoop”). The hoop 102 is sized and shaped forbeing circumferentially disposed about a burr hole (which, in thisdocument, is understood to include a twist drill hole) or other entryportal of a desired size. Burr holes typically range in diameter betweenabout 6 millimeters to about 14 millimeters. In this example, hoop 102includes holes 104A-B or other passages for receiving corresponding bonescrews or the like therethrough for securing hoop 102 to a subject'sskull (or other desired location upon the subject). In this example,hole 104A is located on an opposite side of hoop 102 from hole 104B. Inoperation, hoop 102 is secured to the skull before the electrode orother instrument is inserted to the desired location in the patient'sbrain. The electrode or other instrument (for example an aspirationcatheter or an infusion catheter) is inserted through the circularcenter passage defined by hoop 102.

In this example, instrument immobilizer 100 includes a two-piece slidingcover including cover pieces 106A-B. Each cover piece 106A-B is sizedand shaped to be inserted through a corresponding side slot 108A-B in anopposing side of hoop 102. Each piece of cover piece 106A-B also has asnap-fit or other catch 109A-B, such as a deformable tab, that engages aportion of hoop 102 when that cover piece 106A or 106B has been fullyinserted. Catches 109A-B hold their corresponding cover piece 106A-B inplace after it has been fully inserted. Alternatively, the instrumentimmobilizer includes a one-piece sliding cover that, in one example, thesingle cover piece substantially covers the circular center passage whenfully inserted through a corresponding side slot.

FIG. 2 is a top view illustrating generally an example of portions ofinstrument immobilizer 100 after cover pieces 106A-B have been partiallyinserted into respective slots 108A-B in opposing sides of hoop 102.FIG. 3 is a perspective view illustrating generally an example ofportions of instrument immobilizer 100 after cover pieces 106A-B havebeen partially inserted into respective slots 108A-B of hoop 102. FIG. 4is a side view illustrating generally an example of portions ofinstrument immobilizer 100 after cover pieces 106A-B have been almostfully inserted into respective slots 108A-B of hoop 102. FIG. 5 is a topview illustrating generally an example of portions of instrumentimmobilizer 100 after cover pieces 106A-B have been fully inserted intorespective slots 108A-B of hoop 102.

As illustrated generally in FIGS. 1-5, when cover pieces 106A-B havebeen fully inserted and pressed against each other, they substantiallycover the center passage defined by hoop 102, except for a smallcircular opening 500 formed by aligned semi-circular cutouts 110A-B ofcover pieces 106A-B. Also, when cover pieces 106A-B have been fullyinserted and their respective beveled edges 112A-B are pressed againsteach other, a resulting trough, channel or groove 502 is formed. In thisexample, groove 502 aligns with exit grooves 114A-B in hoop 102,however, this is not required. In another example, one or more exitgrooves 114A-B are disposed elsewhere about hoop 102, such as, forexample, exit grooves 114 distributed about hoop 102 at regularintervals (e.g., every 30 degrees, etc.). Moreover, such differentlydisposed exit grooves 114 are also applicable to all of the otherexamples depicted and/or described in this document.

FIG. 22 is a top view illustrating an instrument immobilizer 100retaining at least one wire electrode or other introduced instrument2200 (e.g., a catheter). Once the instrument 2200 is retained by coverpieces 106A-B so as to immobilize the instrument, a portion of theinstrument 2200 may be bent into a portion of groove 502 and one of exitgrooves 114A-B to laterally exit hoop 102. In the above describedexample having multiple exit grooves 114A-B, the instrument 2200 may bebent into any one of the exit grooves 114A-B. The introduced instrument2200 is retained and immobilized by the snug fit through opening 500.Additionally the instrument 2200 is further retained by snug positioningof a portion of the instrument 2200 within the groove 502 and one of theexit grooves 114A-B. Where the instrument 2200 is positioned within anexit groove 114A-B the instrument immobilizer 100 and instrument 2200,in one example, are covered by a cap that provides a semi-permanentfixture for both.

FIGS. 6-9 and 23 illustrate various views of a second embodiment of alow-profile instrument immobilizer for securing a flexible recording orstimulating electrode or the like (or other instrument, such as acatheter) after it has been introduced through a burr hole or otherentry portal to a desired target location in the brain.

FIG. 6 is a perspective view illustrating generally, by way of example,but not by way of limitation, portions of instrument immobilizer 600. Inthis example, instrument immobilizer 600 includes a base 602 sized andshaped for being secured above and covering a similarly-sized burr holeor other entry portal. In this example base 602 includes a pair ofsemicircular pieces 602A-B. Base 602 includes holes 604A-B or otherpassages for receiving corresponding bone screws or the liketherethrough for securing base 602 to a subject's skull (or otherdesired location upon the subject). In this example, hole 604A islocated on an opposite side of base 602 from hole 604B. The holes 604A-Bare, in this example, located on members 605A-B, which extend radiallyoutward from base 602. In one example of operation, base 602 is securedto the skull by inserting a screw through one of the holes 604A-B. Thispermits the instrument immobilizer 600 to rotate about the axis of thescrew through the one of the holes 604A-B. The instrument immobilizer600 is rotated away from the burr hole in this manner, thereby providingaccess to the burr hole. The electrode or other instrument is insertedthrough the burr hole to the target location, as desired. The instrumentimmobilizer is then rotated back toward the burr hole about the axis ofthe screw through the one of the holes 604A-B such that the instrumentextends through an access slot 606. The instrument can then be furthersecured, such as discussed below.

In this example, the access slot 606 extends across base 602, except forthe presence of connecting member 608. The slot 606 permits access tothe underlying burr hole or other entry portal, except for theobstruction of connecting member 608. Connecting member 608 provides amechanical connection between two semicircular portions 602A-B of base602. The semicircular portions 610A-B are separated by slot 606 andconnecting member 608.

In this example, a latch 610 is eccentrically coupled to base 602 bycoupling the latch to the base at a point offset from the center of thebase. In the example of FIG. 6, the latch includes a semicircular latchpiece 610 having a post 616 that is snap-fit into semicircular piece602A of base 602. FIG. 6 illustrates latch piece 610 in aneccentrically-mounted open position. In this example, latch piece 610includes a semicircular notch or cutout 612 that is sized to retain theelectrode or other instrument snugly within slot 606 when latch piece610 is moved to the closed position. After the instrument is axiallypositioned as desired within the slot 606, then the latch piece 610 ismoved to the closed position and immobilizes the instrument. FIG. 7 is aside view of instrument immobilizer 600 with latch piece 610 in the openposition. FIG. 8 is a perspective view of instrument immobilizer 600with latch piece 610 in the closed position. FIG. 9 is a side view ofinstrument immobilizer 600 with latch piece 610 in the closed position.

In FIGS. 6-9, when latch piece 610 is in the closed position thesemicircular shape of latch piece 610 aligns and conforms with thecircumference of base 602 such that the peripheral profile of the latchpiece 610 is coextensive with the peripheral profile of the base 602when the immobilizer 600 is viewed from above.

FIG. 23 is a perspective view illustrating the instrument immobilizerretaining a wire electrode or other introduced instrument 2200 (forexample a catheter as described above). In the closed position, theinstrument 2200 is snugly retained within the semicircular cutout 612between latch piece 610 and connecting member 608. In this example, thelatch piece 610 is securable in the closed position by a detent 616 thatextends from a lower surface of the latch piece 610. As generally shownin FIG. 6, the detent 616 engages the base 602 within a securing slot618 defined by the base to secure the latch piece 610 in the closedposition. The instrument 2200 may be laterally bent (e.g., such as atabout a 90 degree angle, or otherwise) to laterally exit base 602. Inthis example, the laterally bent portion of the instrument 2200 may bewedged snugly under or along a tab (such as retaining member 614)disposed above slot 606. This further secures the instrument 2200 afterimmobilization by the latch piece 610.

FIGS. 10-14 illustrate various views of a third embodiment of alow-profile instrument immobilizer for securing a flexible recording orstimulating electrode or the like, or other instrument, after it hasbeen introduced through a burr hole or other entry portal to a desiredtarget location in the brain.

FIG. 10 is a top view illustrating generally, by way of example, but notby way of limitation, portions of instrument immobilizer 1000. In thisexample, instrument immobilizer 1000 includes a base 1002 sized andshaped for being secured such that it is cantilevered over at least aportion of a burr hole or other entry portal. In this example base 1002includes a pair of approximately semicircular portions 1002A-B connectedby connecting member portions 1002C-D. Base 1002 includes holes 1004A-Bor other passages for receiving corresponding bone screws or the liketherethrough for securing base 1002 to a subject's skull (or otherdesired location upon the subject). An optional slot or lateral groove1006 extends between semicircular portions 1002A-B and connecting memberportions 1002C-D of base 1002.

In this example, instrument immobilizer 1000 includes a semicircularshaped clasp 1008. The clasp 1008 is coupled at a first end to one ofthe semicircular portions 1002A-B by a hinge 1010. At a second end, theclasp 1008 includes a fastener 1012. In this example, the fastener 1012includes a male snap-fitting, for securing to a mating female receptacle1100 (FIG. 11) in the other of the semicircular portions 1002A-B whenthe clasp 1008 is moved from an open position to a closed position. Inanother example, the clasp 1008 is coupled at a first end to one of thesemicircular portions 1002A-B with a flexible element, including but notlimited to deformable plastic, or a hinge as described above. FIG. 11 isa top view of instrument immobilizer 1000 with clasp 1008 in the closedposition. FIG. 12 is a perspective view of instrument immobilizer 1000with clasp 1008 in its closed position. FIG. 13 is a side view ofinstrument immobilizer 1000 with clasp 1008 in its open position. FIG.14 is a side view of instrument immobilizer 1000 with clasp 1008 in itsclosed position.

FIG. 24 is a perspective view of an instrument immobilizer retaining awire electrode or other instrument 2200 (for example, a catheter foraspiration or substance infusion). The instrument immobilizer base 1002is secured to the skull such that clasp 1008 is cantilevered over theburr hole or other entry portal. The electrode or other instrument isinserted through the burr hole or other entry portal to the desiredlocation so the instrument is near the clasp 1008. In one option, theinstrument is adjacent a side surface of the instrument immobilizer1000. The clasp 1008 is then closed around the electrode or otherinstrument to snugly retain it. The electrode or other instrument islaterally bent into lateral groove 1006 and positioned snugly undercantilevered retaining members 1014A-B extending from semicircularportions 1002A-B over lateral groove 1006. As shown in FIG. 24, Theelectrode or other instrument is thereby immobilized by clasp 1008.Cantilevered retaining members 1014A-B and/or lateral groove 1006 aresized or otherwise configured to snugly conform to the electrode orother instrument. This provides additional snug retention of theelectrode or other instrument.

FIGS. 15-16 illustrate various views of a fourth embodiment of alow-profile instrument immobilizer for securing a flexible recording orstimulating electrode or the like, or other instrument (a catheter, inone example), after it has been introduced through a burr hole or otherentry portal to a desired target location in the brain.

FIG. 15 is a perspective view illustrating generally, by way of example,but not by way of limitation, portions of instrument immobilizer 1500for securing an electrode 1502 or other instrument. In this example,instrument immobilizer 1500 includes a two-piece base 1504A-B. Basepiece 1504A is sized and shaped for being disposed along a first side ofa burr hole 1505 or other entry portal. Base piece 1504B is sized andshaped for being disposed along a second side of a burr hole or otherentry portal. Each elongated base piece 1504A-B includes a correspondinghole 1506A-B, at a first end, for receiving a corresponding bone screw1508A-B or the like therethrough for securing the corresponding basepiece 1504A-B to the subject's skull. In one example, the bone screws1508A-B and holes 1506A-B are disposed on opposite sides of the burrhole 1505. In another example, the base pieces 1504A-B are sized andshaped so bone screws 1508A-B and holes 1506A-B are disposed atnon-opposed locations around the burr hole 1505. Each bone screw 1508A-Band corresponding hole 1506A-B provides a hinge about which thecorresponding elongate base piece 1504A-B rotates, such as from the openposition illustrated in FIG. 15 to a closed position, in which basepieces 1504A-B retain and immobilize the electrode or other instrument.In one option, the base pieces 1504A-B rotate about parallel axes. Inanother option the base pieces 1504A-B rotate within the same plane.FIG. 16 is a top view illustrating base pieces 1504A-B in a closedposition, retaining and immobilizing a laterally bent electrode 1502. Inthe example of FIGS. 15-16, base pieces 1504A-B are disposed such thatwhen these pieces are rotated into the closed position of FIG. 16, malecouplers 1508A-B (for example snap fittings) on base piece 1504A engagecorresponding mating couplers 1510A-B on base piece 1504B. This fastensbase pieces 1504A-B together to retain electrode 1502 therebetween.Electrode 1502 is further laterally bent into the groove 1512 of basepiece 1504A. Groove 1512 is sized and shaped to snugly grasp electrode1502 therein to further retain and immobilize electrode 1502.

FIG. 17 is a top view illustrating generally, by way of example, but notby way of limitation, a fifth embodiment of an instrument immobilizer,such as instrument immobilizer 1700. In this example, instrumentimmobilizer 1700 includes a hoop-like base 1702 (also referred to hereinas a “hoop”) sized and shaped for being circumferentially disposed abouta burr hole or other entry portal of a desired size. In this example,hoop 1702 includes holes 1704A-B or other passages for receivingcorresponding bone screws or the like therethrough for securing hoop1702 to a subject's skull (or other desired location upon the subject).In this example, hole 1704A is located on an opposite side of hoop 1702from hole 1704B.

In this example, hoop 1702 defines a center passage therewithin, intowhich an insert 1706 is disposed. Insert 1706 includes at least onesnap-fitting feature that allows insert 1706 to be snapped into hoop1702. In one example, insert 1706 is inserted into the circular centerpassage of hoop 1702 such that insert 1706 rotates therewithin withrespect to hoop 1702. In this example, the insert 1706 includes at leastone detent disposed about the insert bottom surface and projecting tothe side of the insert. The hoop 1702 includes a corresponding groovedsurface disposed upon an intermediate surface therein. The at least onedetent engages the grooved surface. This engagement prevents unwantedrotation of the insert 1706 with respect to the hoop 1702.

In FIG. 17, insert 1706 includes a rectangular or other access opening1708. Retaining members 1710A-B are movably coupled to the insert 1706.In one example, the retaining members 1710A-B, include slidableretaining members carried substantially within access opening 1708. Inone example, access opening 1708 includes opposing side slide rails thatallow retaining members 1710A-B to slide toward and away from each otherwithin access opening 1708. In the example of FIG. 17, sliding retainingmembers 1710A-B each have beveled edges 1712A-B and semicircular cutouts1714A-B in center portions of beveled edges 1712A-B. When retainingmembers 1710A-B are positioned adjacent to each other, beveled edges1712A-B form a lateral groove, and semicircular cutouts 1714A-B arealigned to each other to form a circular opening. In an alternativeexample, however, the semicircular cutouts 1714A-B are omitted.

In one example, retaining members 1710A-B include respective matingcouplings to hold the retaining members in engagement with each other.In one option, the mating couplings include snap-fit features tomaintain engagement between the retaining members 1710A-B. In anotherexample, at least one of the retaining members 1710A-B includes anengagement coupling that secures the at least one of the retainingmembers 1710A-B relative to insert 1706. In one option, the engagementcoupling includes a “one-way” toothed surface disposed substantiallyupon the side slide rails of the insert 1706. Corresponding tabs aredisposed along the bottom edge of the at least one of the retainingmembers 1710A-B. The tabs engage the toothed surface and thereby allowslidable movement of the at least one of the retaining members 1710A-Bin one direction, typically toward the other retaining member.

In another option, both retaining members 1710A-B have tabs that engagetoothed surfaces on the rails. When retaining members 1710A-B contacteach other, the tabs engaging the toothed rails maintain engagementbetween the retaining members 1710A-B. The retaining members 1710A-B donot disengage from each other because the tabs and teeth prevent slidingaway in the other direction. If it is desirable to move the retainingmembers 1710A-B in a direction counter to that allowed by the tabs andteeth the retaining members 1710A-B are pulled out of engagement withthe side rails, disengaged from each other and repositioned within theside slide rails.

FIG. 18 is a top view illustrating instrument immobilizer 1700 retaininga wire electrode or other instrument 2200. In operation, hoop 1702 issecured and insert 1706 is inserted therein. An electrode or otherinstrument 2200 (for example an aspiration or infusion catheter) isinserted between retaining members 1710A-B to the desired location inthe patient's brain. In one example, the insert 1706 is capable of beingrotated about the instrument 2200. This provides added flexibility inthe location for immobilization of the instrument. Retaining members1710A-B are moved against each other to snugly retain and immobilize aportion of the instrument 2200, such as within the circular openingdefined by semicircular cutouts 1714A-B. In another example, thesemicircular cutouts 1714A-B are omitted and the instrument 2200 iscompressibly retained between the beveled edges 1712A-B at a desiredposition anywhere along the beveled edges. The retaining members 1710A-Bengage each other and/or the side rails (as discussed above) toimmobilize the instrument 2200. If desired, the instrument 2200 can bebent into the lateral groove formed 1800 by beveled edges 1712A-B. Inone example, the lateral groove 1800 aligns with one or more lateralexit grooves 1716A-B providing lateral access through hoop 1702,allowing the electrode or other instrument to laterally exit hoop 1702.In one example, the lateral groove 1800 and/or the lateral exitgroove(s) 1716A-B are sized and shaped to snugly grasp and retain theinstrument 2200. In another example, once the instrument 2200 isimmobilized by the retaining member 1710A-B and grasped and retained bythe lateral groove 1800 and/or lateral exit groove 1716A-B, a cap isaffixed to the instrument immobilizer 1700.

FIG. 19 is a top view illustrating generally, by way of example, but notby way of limitation a sixth embodiment of an instrument immobilizer,such as instrument immobilizer 1900. In this example, instrumentimmobilizer 1900 includes a hoop-like base 1902 (also referred to hereinas a “hoop”) sized and shaped for being circumferentially disposed abouta burr hole or other entry portal of a desired size. In this example,hoop 1902 includes holes 1904A-B or other passages for receivingcorresponding bone screws or the like therethrough for securing hoop1902 to a subject's skull (or other desired location upon the subject).In this example, hole 1904A is located on an opposite side of hoop 1902from hole 1904B.

In this example, hoop 1902 defines a center passage therewithin, intowhich a lid 1906 is disposed. Lid 1906 includes at least onesnap-fitting feature that allows lid 1906 to be snapped into hoop 1902.In one example, lid 1906 rotates substantially within the circularcenter passage of hoop 1902. In another example, the lid 1906 includesat least one detent on its bottom surface, and the hoop 1902 includes acorresponding groove on or near its inner periphery. The at least onedetent engages the groove. This prevents undesirable rotation of the lid1906 with respect to the hoop 1902.

In this example, the lid 1906 includes a slot 1908. In one option, theslot 1908 has an arcuate geometry defined by the lid 1906 and extendsacross an angle of approximately 15 degrees. The slot 1908 extends froman outer edge 1920 of the lid 1906, tapering inward toward a center 1922of the lid 1906. The slot includes at least one socket 1910. FIG. 19illustrates the socket 1910 extending through the center of the lid1906. However, the socket 1910 may alternatively be offset from thecenter of the lid 1906 to provide added flexibility in positioning andimmobilizing an instrument. In one example, the slot 1908 narrows as itextends from the outer edge 1920 of the lid 1906 toward the socket 1910.In FIG. 19, just before reaching the socket 1910, the slot 1908 isslightly more narrow than the socket 1910 is wide. This provides a lip1912 on the slot 1908 adjacent the socket 1910.

FIG. 20 is a top view illustrating a wire electrode or other instrument2200 (e.g., a catheter, such as for aspiration or infusion of drug(s),cell(s) or other substances) that is immobilized by the instrumentimmobilizer 1900. In one example of operation, hoop 1902 is firstsecured. The instrument 2200 is then inserted through the hoop 1902 tothe desired location in the patient's brain. In one example, the lid1906 is then inserted into the hoop 1902 such that the instrument 2200is disposed within a slot 1908. Inserting the lid 1906 after positioningthe instrument 2200 provides additional flexibility for positioning theslot around the instrument 2200 so as to reduce or minimize any unwantedmovement of the instrument 2200. The instrument 2200 is then advancedlaterally within the slot 1908 toward the socket 1910. Upon reaching thelip 1912, a portion of the instrument 2200 and/or the lip 1912 deformsslightly to permit the instrument 2200 to enter the socket 1910 forretention and immobilization by the socket 1910. In one example, thehoop 1902 includes at least one lateral exit groove 1916 and the lid1906 includes at least one lateral exit groove 1918. The lid 1906 ispositionable to permit groove 1918 to align with one of the lateral exitgrooves 1916. A portion of the instrument 2200 is then bent andpositioned within the groove 1918 and lateral exit groove 1916 where itis retained snugly therein. This further immobilizes the instrument2200. In one example, a cap is affixed to the instrument immobilizer1900.

FIG. 21 is a perspective view of another embodiment of a lid 2100 usablewith the instrument immobilizer 1900 illustrating generally multipleslots 2102, sockets 2104 and lips 2106. The lid 2100, as illustrated inthe example of FIG. 21, is operable to retain and immobilize up to threeinstruments. Alternately, the lid 2100 is operable to retain aninstrument in multiple positions for flexibility of immobilization.Similar configurations can be used to immobilize fewer or greaterinstruments.

FIG. 25 is a perspective view illustrating generally, by way of example,but not by way of limitation a seat assembly 2500. In this example, theseat assembly 2500 includes a seat 2502 sized and shaped for beingdisposed within a burr hole. In one example, the seat has a geometrycorresponding to the burr hole, for example a circular shape. In anexample, the seat 2502 is constructed from a deformable material havinga shape memory property, for example a thermoplastic, which goes by thetrade name GRILAMID, and is registered to EMS-Grivory. In anotherexample, the seat 2502 is constructed with polycarbonate. In anotherexample, the seat 2502 includes prongs 2504. The prongs 2504, in oneoption, are joined substantially adjacent to a bridge 2506. In oneexample, as shown with arrows 2508, the prongs 2504 are deformable. Inanother example, the prongs 2504 are pinched and the ends of the prongs2504 move into the gap 2510. When released, the prongs 2504 expand backtoward their original position. In one example, the prongs 2504 arepinched together while inserting the seat assembly 2500 within the burrhole. The prongs 2504 are then released to expand so the outer surfacesof the prongs 2504 engage the inner cylindrical surface defining theburr hole to snugly hold the seat assembly 2500 within the burr hole. Instill another example, cavities 2512 are provided in the ends of theprongs 2504. The cavities 2512 allow forceps, or the like, to grasp andpinch the prongs 2504 by inserting the forceps into the cavities 2512.

The seat assembly also includes a collar 2514 coupled to the seat 2502by the bridge 2506. In one example, the collar 2514 is suspended withinthe burr hole by the bridge 2506. In other words, the collar 2514 issuspended within a space 2516 defined by the inner surfaces of the seat2502. In an alternative embodiment, the collar 2514 is disposed above orbelow the plane defined by the seat 2502. Optionally, where the collar2514 is disposed below or above the seat 2502 at least the outer surfaceof the collar 2514 may have a greater circumference than the innersurface of the seat 2502. In another example, the bridge 2506 spans adistance between the seat 2502 and the collar 2514 substantially equalto the distance between the inner surface of the seat 2502 and the outersurface of the collar 2514. In one example, the collar 2514 is spacedfrom the seat 2502 so where the prongs 2504 are in an undeformed ordeformed condition they do not contact the collar 2514. In an example,the collar 2514 defines a socket 2518 and is dimensioned and configuredto retain an instrument immobilizer seated therein, for exampleinstrument immobilizer insert 1706. In still another example, the seatassembly 2500 and instrument immobilizer insert 1706 are integral toeach other.

FIG. 26 is a top view showing instrument immobilizer insert 1706 seatedwithin the socket provided by the collar 2514 of the seat assembly 2500.In one example, the collar 2514 includes a slit 2600 sized and shaped topass an instrument therethrough. The instrument immobilizer insert 1706,in another example, includes a corresponding slit 2602 sized and shapedto pass an instrument between the retaining members 1710A-B. The slit2602 is aligned with the slit 2600 to permit movement of the instrumentfrom outside the collar 2514 toward the retaining member 1710A, B.Optionally, the collar 2514 is dimensioned and configured to retain avariety of instrument immobilizer inserts, including, but not limitedto, inserts configured like instrument immobilizers 100, 600, 1000,1500, or 1900 and lid 2100. In one option, when using the seat assembly2500 bone screws are not needed as the instrument immobilizer is snuglyretained by the collar 2514 and the seat 2502 is retained within theburr hole by the prongs 2504.

FIG. 27 is an exploded view showing one example of a burr hole 2700,seat assembly 2500, instrument immobilizer insert 1706 and cap 2701. Inthis example, the burr hole 2700 includes a countersink 2702. At least aportion of the inner surface 2704 of the burr hole 2700 and a shelf 2706within the burr hole 2700 define the countersink 2702. In one example,the lower surface of the seat 2502 is disposed on the shelf 2706 and theouter surfaces of the prongs 2504 are snugly coupled to the innersurface 2704 of the burr hole 2700. In another example, the cap 2701 isdisposed over the instrument immobilizer and snugly coupled to theinstrument immobilizer and/or the seat assembly 2500. Optionally, thecap 2701 covers the instrument immobilizer and an instrument immobilizedtherein and provides a semi-permanent fixture for both. In anotheroption, the cap 2701 is constructed with a biocompatible polymer (e.g.santoprene, polyurethane, silicone or the like). In yet another option,the cap 2701 is constructed with a deformable material so the cap 2701may be press fit around the seat assembly 2500. The seat assembly 2500and the instrument immobilizer insert 1706 optionally include slits2600, 2602 as shown in FIG. 26 and described above.

FIG. 28 is a perspective view of another example of a seat assembly2800. In one example, the seat assembly 2800 is substantiallycylindrical and dimensioned and configured to snugly couple with aninner surface of a burr hole. In one option, the burr hole has asubstantially cylindrical geometry corresponding to the seat assembly2800. In another example, the seat assembly 2800 includes threading 2802along an outer surface of the seat assembly 2800 for securing the seatassembly 2800 within the burr hole. Optionally, the threading 2802 isself tapping and correspondingly threads the bone surface defining theburr hole as the seat assembly 2800 is inserted in the burr hole. In yetanother example, the outer surface of the seat assembly 2800 is smoothand is dimensioned and configured to be press fit into the burr hole.

An inner surface of the seat assembly 2800 defines an access lumen 2804.In one option, the access lumen 2804 is dimensioned and configured so aninstrument immobilizer, for example, instrument immobilizer insert 1706is capable of being disposed within the access lumen 2804. In yetanother example, the seat assembly 2800 includes a collar 2806. In oneoption, the collar 2806 extends from the inner surface of the seatassembly 2800 and forms an annular ridge within the access lumen 2804.In another option, the collar 2806 is a discontinuous flange within theaccess lumen 2804. The collar 2806 is dimensioned and configured tocouple with an instrument immobilizer such as instrument immobilizerinsert 1706. In one example, the collar 2806 includes at least one snapfitting 2805 sized and shaped to engage with a corresponding projection,such as snap fitting 2807, on the instrument immobilizer insert 1706 toretain the insert 1706 in the collar 2806. The snap fitting 2805 definesa socket and is sized and shaped to receive the snap fitting 2807. Inanother example, the collar 2806 is dimensioned and configured to retaina variety of instrument immobilizer inserts, including, but not limitedto, inserts configured like instrument immobilizers 100, 600, 1000,1500, or 1900 and lid 2100.

In one option, when the seat assembly 2800 is inserted within the burrhole the seat assembly 2800 is substantially flush with the surface ofthe skull or disposed beneath the surface of the skull. In anotheroption, when the instrument immobilizer insert 1706 is coupled to theseat assembly 2800 and the seat assembly 2800 is inserted within theburr hole, the insert 1706 is substantially flush with the surface ofthe skull or disposed beneath the surface of the skull. Optionally, theseat assembly 2800 and instrument immobilizer insert 1706 present noprofile above the surface of the skull when inserted within the burrhole.

In another example, the seat assembly 2800 includes tool cavities 2808.In one option, the multiple tool cavities 2808 are formed in an endsurface 2810 of the seat assembly 2800. In another option, the toolcavities 2808 are dimensioned and configured to receive the tines of adriving instrument. Optionally, the driving instrument is used to turnthe threaded seat assembly 2800 and screw the seat assembly 2800 intothe burr hole.

FIG. 29 is a perspective view of yet another example of a seat assembly2900. In some respects, seat assembly 2900 is similar to seat assembly2800. In one example, seat assembly 2900 includes threading 2902 similarto seat assembly 2800. In one option, the threading 2902 is self tappingand correspondingly threads the bone surface defining the burr hole asthe seat assembly 2800 is inserted in the burr hole. The seat assembly2900 includes a flange 2903. In one example, the flange 2903 extendsradially from an access lumen 2905 and has a sloping geometry to createa smooth profile over the skull when the seat assembly 2900 is disposedwithin the burr hole. In another example, the flange 2903 is an annularridge extending around the seat assembly 2900.

In another example, the flange 2903 includes tool cavities 2904. Thetool cavities 2904 are dimensioned and configured to receive the tinesof a driving instrument. Optionally, the driving instrument is used toturn the threaded seat assembly 2900 and screw the seat assembly 2900into the burr hole. The flange 2903 serves as a depth stop as the seatassembly 2900 is driven into burr hole. In one option, the flange 2903positions the seat assembly 2900 at a predetermined depth within theburr hole.

FIG. 30 is an exploded view of still another example of a seat assembly3000. In some respects, seat assembly 3000 is similar to seat assemblies2800, 2900. Seat assembly 3000 includes tool cavities 3002 that extendthrough the flange 3004. In another option, the tool cavities 3002receive fasteners such as screws 3006 or the like that are driven intothe skull. The screws 3006 secure the seat assembly 3000 to the skull.The outer surface of the seat assembly 3000 is smooth and is dimensionedand configured to be press fit into a burr hole. The press fitengagement of the seat assembly 3000 temporarily retains the seatassembly 3000 within the burr hole. Optionally, the seat assembly 3100is then securely coupled to the surface around the burr hole withfasteners, such as screws 3006, described above. Optionally, the outersurface of the seat assembly 3000 includes threading similar to theouter surfaces of the seat assemblies 2800, 2900, described above.

FIG. 31A is an exploded view of another example of a seat assembly3100A. In one example, the seat assembly 3100A is cylindrical anddimensioned and configured to snugly couple with an inner surface of theburr hole 3103. In another example, the seat assembly 3100A includesthreading 3106 along an outer surface for securing the seat assembly3100A within the burr hole 3103. In yet another example, the outersurface of the seat assembly 3100A is smooth and is dimensioned andconfigured to be press fit into the burr hole 3103. In still anotherexample, seat assembly 3100A includes tool cavities 3102 in an endsurface 3104. As described above with the seat assemblies 2800, 2900,3000, the tool cavities 3102 are dimensioned and configured to receivethe tines of a driving instrument for inserting the seat assembly 3100Awithin the burr hole 3103.

An inner surface of the seat assembly 3100A defines an access lumen3111. In one example, an instrument immobilizer, for example, instrumentimmobilizer insert 1706 is coupled to the seat assembly 3100A anddisposed above the access lumen 3111. In one option, the instrumentimmobilizer insert 1706 has an outer perimeter substantiallycorresponding to the outer perimeter of the seat assembly 3100A. As aresult, the instrument immobilizer insert 1706 has an outer perimetersubstantially corresponding to an inner perimeter of the burr hole 3103.Optionally, the instrument immobilizer insert 1706 has a diameter ofabout 14 millimeters.

Optionally, at least one of the seat assembly 3100 and the insert 1706includes projections and/or sockets sized and shaped to couple theinsert 1706 with the seat assembly 3100 by a snap fit. In one example,the instrument immobilizer insert 1706 includes projections, such asposts 3108, extending from one face of the insert 1706. In one option,the posts 3108 are dimensioned and configured to snugly fit within thetool cavities 3102. In another option, the posts 3108 include snapfittings 3110. In yet another option, the tool cavities 3102 includecorresponding sockets 3112 dimensioned and configured to receive thesnap fittings 3110. The snap fittings 3110 and sockets 3112 aredimensioned and configured to snugly couple the instrument immobilizerinsert 1706 to the seat assembly 3100. In another example, the seatassembly 3100 is dimensioned and configured to snugly couple with avariety of instrument immobilizer inserts, including, but not limitedto, inserts configured like instrument immobilizers 100, 600, 1000,1500, or 1900 and lid 2100.

FIG. 31B shows another example of a seat assembly 3100B. The instrumentimmobilizer insert 1706 has a slightly smaller outer perimeter than theouter perimeter of the seat assembly 3100B. The instrument immobilizerinsert 1706 is coupled to the inner surface of the seat assembly 3100Bthat defines the access lumen 3111. In one example, the seat assembly3100B includes an annular ridge on the inner surface that defines acollar 3114. The collar 3114 includes at least one snap fitting 3116sized and shaped to engage with a corresponding projection, such as snapfitting 3118, on the instrument immobilizer insert 1706 to retain theinsert 1706 in the collar 3114. The snap fitting 3116 defines a socketand is sized and shaped to receive the snap fitting 3118. In anotherexample, the collar 2806 is dimensioned and configured to retain avariety of instrument immobilizer inserts, including, but not limitedto, inserts configured like instrument immobilizers 100, 600, 1000,1500, or 1900 and lid 2100.

In another example, the seat assembly 3100B includes a cap 3120 sizedand shaped to cover the instrument immobilizer insert 1706. At least oneof the seat assembly 3100B and the cap 3120 includes projections and/orsockets sized and shaped to couple the cap 3120 with the seat assembly3100B by a snap fit. In one option, the cap 3120 includes projections,such as posts 3108, extending from one face of the cap 3120. In oneoption, the posts 3108 are dimensioned and configured to snugly fitwithin tool cavities 3102. In another option, the posts 3108 includesnap fittings 3110. In yet another option, the tool cavities 3102include corresponding sockets 3112 dimensioned and configured to receivethe snap fittings 3110. The snap fittings 3110 and sockets 3112 aredimensioned and configured to snugly couple the cap 3120 to the seatassembly 3100B.

FIG. 31C shows another example of a seat assembly 3100C. The seatassembly 3100C has an integral instrument immobilizer such as instrumentimmobilizer 1706. In one option, the instrument immobilizer 1706 isformed with the rest of the seat assembly 3100C (e.g., by molding,machining and the like). In another option, the instrument immobilizer1706 is bonded with the seat assembly 3100C with adhesives, welds (e.g.,ultrasonic welding) and the like. In yet another example, the seatassembly 3100C includes a variety of integral instrument immobilizers,including, but not limited to, immobilizers configured like instrumentimmobilizers 100, 600, 1000, 1500, or 1900 and lid 2100. The seatassembly 3100B, in still another example, includes a cap such as cap3120 (FIGS. 31A, B) sized and shaped to cover the instrument immobilizer1706.

Referring again to FIGS. 31A-C, in one example, when the seat assembly3100A-C is inserted within the burr hole the seat assembly 3100A-C issubstantially flush with the surface of the skull or disposed beneaththe surface of the skull. In another option, when the instrumentimmobilizer insert 1706 is coupled to the seat assembly 3100A, B and theseat assembly 3100A, B and insert 1706 are inserted within the burrhole, the insert 1706 and/or the seat assembly 3100A, B aresubstantially flush with the surface of the skull or disposed beneaththe surface of the skull. Optionally, the seat assembly 3100A-C andinstrument immobilizer insert 1706 present no profile above the surfaceof the skull when inserted within the burr hole.

In the above examples (aspects of which can be combined with eachother), the components of instrument immobilizers 100, 600, 1000, 1500,1700, 1900, lid 2100, and seat assemblies 2500, 2800, 2900, 3000, 3100may be manufactured from molded plastic and are MRI compatible. The bonescrews used for securing the instrument immobilizers may be manufacturedfrom stainless steel. In one example, such bone screws include imagingfiducial markers integral or attachable thereto. Additionally, in otherembodiments of the above examples the exit grooves are disposed atvarious locations (for example, at regular intervals) about theinstrument immobilizers 100, 600, 1000, 1500, 1700, and 1900 to provideflexibility in the placement of the instruments when immobilized.Instrument immobilizers 100, 600, 1000, 1500, 1700, 1900, lid 2100, andseat assemblies 2500, 2800, 2900, 3000, 3100 are not limited to use inconjunction with skull burr holes in neurosurgery, but may be secured atother locations of a patient for securing an electrode or other surgicalinstrument (for example catheters used for aspiration or infusion), orabout or within an entry portal in other objects into which aninstrument has been introduced, and which requires immobilization. Theabove examples provide instrument immobilizers that are designed toadvantageously provide a low-profile (e.g., small height) above or flushto the patient's skull. By way of example, but not by way of limitation,in one embodiment, instrument immobilizer 100 provides a height of lessthan about 0.1 inches, instrument immobilizer 600 provides a height ofless than about 0.08 inches, instrument immobilizer 1000 provides aheight of less than about 0.08 inches, instrument immobilizer 1500provides a height of less than about 0.065 inches, instrumentimmobilizer 1700 provides a height of less than about 0.1 inches,instrument immobilizer 1900 and lid 2100 provide a height of less thanabout 0.1 inches, and seat assemblies 2500, 2800, 3100 and instrumentimmobilizer 1700 provide a height of 0.0 inches.

FIG. 32 is a block diagram of a method 3200 for immobilizing aninstrument, for example an electrode or catheter. At 3202, an instrumentis disposed within a passage of an instrument immobilizer base. At 3204,a first cover piece and a second cover piece are advanced toward theinstrument as shown, for example, in FIGS. 1 and 22 with the instrumentimmobilizer 100 having cover pieces 106A, 106B. At 3206 the first coverpiece and the second cover piece are engaged against the instrument toimmobilize the instrument therebetween.

Several variations are possible. One example includes sliding the firstcover piece through a slot in the instrument immobilizer base andsliding the second cover piece through another slot in the instrumentimmobilizer base. Another example includes grasping and/or retaining aportion of the instrument within a groove defined by the first andsecond cover piece.

FIG. 33 is a block diagram of a method 3300 for immobilizing aninstrument. At 3302, an instrument is disposed within a passage of aninstrument immobilizer base. At 3304, a latch including a notch isrotated toward the instrument as shown, for example, in FIGS. 6 and 23with the instrument immobilizer 600 having the latch 610 and the notch612. At 3300 the instrument is engaged against the latch to immobilizethe instrument, where the surface defining the notch engages theinstrument.

Several variations are possible. One example includes retaining thelatch against the instrument by engaging a portion of the latch to amating portion of the instrument immobilizer base. In another example, aportion of the instrument is laterally positioned against the instrumentimmobilizer base, and the portion of the instrument is tucked under anoverlying retaining member that holds the portion of the instrumentagainst the instrument immobilizer base.

FIG. 34 is a block diagram of a method 3400 for immobilizing aninstrument. At 3402, an instrument immobilizer base is cantileveredabove a burr hole as shown, for example, in FIGS. 10 and 24 with theinstrument immobilizer 1000. At 3404, the instrument is disposed near aside of the instrument immobilizer base. In one example, the instrumentis disposed adjacent a side of the instrument immobilizer base. At 3406the clasp is advanced around the instrument by rotating the clasp abouta first end of the clasp. At 3408, another end of the clasp is engagedwith the instrument immobilizer base to immobilize the instrument.

Several variations are possible. One example includes positioning aportion of the instrument laterally against the instrument immobilizerbase, and tucking the instrument under a retaining member overlying theinstrument and a groove. Another example includes snap-fitting the claspto the instrument immobilizer base.

FIG. 35 is a block diagram of a method 3500 for immobilizing aninstrument. At 3502, an instrument is positioned between a first basepiece and a second base piece as shown, for example, in FIGS. 15 and 16with the instrument immobilizer 1500 having base pieces 1504A, 15048. At3504, the first base piece is rotatably advanced toward the instrument.In one example, the first base piece is rotatably coupled to a surface.At 3506, the first base piece and the second base piece are engagedagainst the instrument to immobilize the instrument therebetween.

Several variations are possible. One example includes rotatablyadvancing the second base piece toward the instrument, where the secondbase piece is rotatably coupled with the surface. Another exampleincludes snapping the first base piece together with the second basepiece. In still another example, a portion of the instrument ispositioned within a groove defined by one of the first base piece or thesecond base piece.

FIG. 36 is a block diagram of a method 3600 for immobilizing aninstrument. At 3602, an instrument is disposed within a passage of aninstrument immobilizer base. At 3604, a first retaining member and asecond retaining member are advanced toward the instrument as shown, forexample, in FIGS. 17 and 18 with the instrument immobilizer 1700 havingthe retaining members 1710A, 1710B. At 3606, the first retaining memberand second retaining member are engaged against the instrument toimmobilize the instrument.

Several variations are possible. One example includes coupling an insertwith an instrument immobilizer base. In another example, a portion ofthe instrument is received along edges of the first and second retainingmember.

FIG. 37 is a block diagram of a method 3700 for immobilizing aninstrument. At 3702, an instrument is disposed within a tapered slot ofan instrument immobilizer base as shown, for example, in FIGS. 19 and 20with the instrument immobilizer 1900 having tapered slot 1908. At 3704,the instrument is moved along the tapered slot until the instrument isgrasped by the tapered slot and immobilized.

Several variations are possible. One example includes disposing a secondinstrument within a second tapered slot of the instrument immobilizerbase, and moving the second instrument along the second tapered slotuntil the second instrument is grasped by the second tapered slot andimmobilized. In another example, a portion of the instrument is receivedlaterally along the instrument immobilizer base.

FIG. 38 is a block diagram of a method 3800 for positioning aninstrument immobilizer. At 3802 a seat is coupled to a surface defininga countersink, such as countersink 2702 shown in FIG. 27. At 3804, theinstrument immobilizer is disposed within a collar coupled to the seatby a bridge. One example of a seat and collar is shown in FIG. 25including the seat 2502 and collar 2514.

FIG. 39 is a side view of a countersinking drill bit 3900. In anotherexample, a countersink is cut around the burr hole. Optionally, couplingthe seat to the surface defining the burr hole includes coupling theseat to the surface defining the countersink. In one example thecountersink is made with the countersinking drill bit 3900 having acentral bore 3902 substantially corresponding in size to the burr holedrilled in a skull. The countersinking drill bit 3900 further includessurrounding blades 3904 that extend from the central bore 3902. Thecentral bore 3902 is inserted within the burr hole and thecountersinking drill bit 3900 is spun and the surrounding blades 3904advanced into the skull to define the countersink. In another example,the countersinking drill bit 3900 includes a depth stop flange 3906above the surrounding blades 3904 to maintain the desired depth of thecountersink.

Several variations are possible. One example includes disposing aninstrument within a passage of the instrument immobilizer. Anotherexample includes advancing a first cover piece and a second cover piece(e.g. first and second cover pieces 1710A, 1710B) toward the instrumentand engaging the first cover piece and the second cover piece againstthe instrument to immobilize the instrument therebetween. Yet anotherexample includes deforming the seat to fit within the burr hole andreleasing the seat so it expands and engages against the surfacedefining the burr hole. Optionally, deforming the seat is performedwithout deforming the collar. In another option, disposing the seatwithin the burr hole is performed prior to disposing the instrumentimmobilizer within the collar.

FIG. 40 is a block diagram of a method 4000 for positioning aninstrument immobilizer. At 4002, a seat is disposed within a burr hole.At 4004, the instrument immobilizer is coupled to a collar of the seatand the instrument immobilizer and/or the seat are flush with an uppersurface around the burr hole (e.g. the outer surface of the skull).Optionally, the instrument immobilizer and/or the seat are below theupper surface. In one example, the inner perimeter of the seat definesan access lumen and the collar extends radially inward into the accesslumen. In another example, the instrument immobilizer substantiallycovers the access lumen. One example of a seat and collar is shown inFIG. 28 including the seat 2800 and collar 2806.

Several variations are possible. One example includes snap fitting theinstrument immobilizer to the collar. Another example includes screwingthe seat into the burr hole. Optionally, the outer perimeter of the seatincludes threading. Yet another example includes coupling the instrumentimmobilizer to the collar of the seat after disposing the seat withinthe burr hole. Another option includes engaging a flange with an uppersurface around the burr hole, wherein the flange extends radially froman outer perimeter of the seat.

FIG. 41 is a block diagram of a method 4100 for positioning aninstrument immobilizer. At 4102, a seat is disposed within a burr hole.Examples of seats are shown in FIGS. 31A-C including the seats 3100A-C.At 4104, the instrument immobilizer is coupled to the seat. Optionally,the instrument immobilizer has an outer perimeter substantiallycorresponding to an inner perimeter of the burr hole. In anotherexample, the seat defines an access lumen. In yet another example, theinstrument immobilizer and/or the seat are flush with the upper surfacearound the burr hole (e.g. the outer surface of the skull). Optionally,the instrument immobilizer and/or the seat are below the upper surface.

Several variations are possible. One example includes snap fitting theinstrument immobilizer to an end surface of the seat. Another exampleincludes disposing a post having a snap fitting within a socketdimensioned and configured to receive the snap fitting. Yet anotherexample includes screwing the seat into the burr hole where the outerperimeter of the seat includes threading. Optionally, coupling theinstrument immobilizer to the seat is performed after disposing the seatwithin the burr hole.

Although the above examples have discussed immobilizing an electrode,these examples are also applicable to immobilizing any other instrument,including, but not limited to instruments for surgical, therapeutic, ordiagnostic use, including use in non-medical fields where immobilizationof an instrument is advantageous. Some examples of such other medicalinstruments include, by way of example, but not by way of limitation, acatheter (e.g., for aspiration or for infusion of a drug, cells, oranother substance), a probe for measuring pressure, temperature, or someother parameter, a biopsy or other needle. Moreover, certain of theabove examples that provide a cover for a burr hole or other entryportal may be useful for serving this function as well, even withoutsecuring and immobilizing an instrument. Further, in some of theexamples above, the instrument immobilizers may be positioned within aburr hole using the seat assembly. Additionally, in other examples, aninstrument immobilizer and the seat assembly may be made integral.Furthermore, in the above examples, one or more of such components maybe coated, impregnated, or otherwise provided with a drug or othertherapeutic agent for delivery to the site at which such component(s)are located. Examples of such agents include steroids or otheranti-inflammatory agents, or anti-infection agents such as antibioticsor antiviral drugs.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments may be used in combination with each other. Many otherembodiments will be apparent to those of skill in the art upon reviewingthe above description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. In the appendedclaims, the terms “including” and “in which” are used as theplain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

1. An apparatus comprising: a first base piece and a second base piece,the first base piece and second base piece each include first and secondends, the first end of the first base piece and the first end of thesecond base piece include respective holes sized and shaped forreceiving a fastener therethrough for rotatable motion thereabout, thesecond end of the first base piece includes at least one coupler sizedand shaped to engage an at least one corresponding coupler disposed onthe second base piece, the first base piece is sized and shaped to bedisposed along a first side of a burr hole and the second base piece issized and shaped to be disposed along a second side of the burr holesuch that the at least one coupler of the first base piece is operableto engage at least one coupler of the second base piece to retain atleast one instrument extending between the first and second base piecesinto the burr hole.
 2. The apparatus of claim 1, in which at least oneof the first and second base pieces includes a lateral exit groove sizedand shaped to retain a portion of the at least one instrument within thegroove.
 3. The apparatus of claim 1, in which the first base piece andthe second base piece rotate about parallel axes.
 4. The apparatus ofclaim 1, in which the first base piece and second base piece rotatewithin substantially the same plane.
 5. The apparatus of claim 1, inwhich the hole in the first end of the first base piece is disposed onan opposing side of the burr hole from the hole in the first end of thesecond base piece.
 6. An apparatus comprising: a first base piece and aseparate second base piece, the first and second base pieces eachincluding an elongated body extending between first and second endsabout a longitudinal axis, the first end of the first base piece and thefirst end of the second base piece including respective holes sized andshaped for receiving a fastener therethrough for rotatable motionthereabout, the second end of the first base piece including at leastone male coupler sized and shaped to engage an at least onecorresponding female coupler disposed on the second end of the secondbase piece, the first base piece being sized and shaped to be disposedalong a first side of a burr hole and the second base piece being sizedand shaped to be disposed along a second side of the burr hole such thatthe hole in the first end of the first base piece is disposed on anopposing side of the burr hole from the hole in the first end of thesecond base piece and the at least one male coupler of the first basepiece is operable to engage the at least one female coupler of thesecond base piece to retain at least one instrument extending betweenthe first and second base pieces into the burr hole.
 7. The apparatus ofclaim 6, wherein the first base piece and the second base piece rotateabout parallel axes extending through a center of the respective holesin the first end of the first and second base pieces and perpendicularto the longitudinal axes of the first and second base pieces.
 8. Theapparatus of claim 6, wherein the at least one male coupler includes apair of male couplers and the at least one female coupler includes acorresponding pair of female couplers, each of the pair of male couplersand the pair of female couplers being spaced apart from each other alongthe longitudinal axis of the respective first and second base pieces. 9.The apparatus of claim 8, wherein the first base piece includes alateral exit channel sized and shaped to retain a portion of the atleast one instrument within the channel, the channel extending along anaxis perpendicular to the longitudinal axis of the body of the firstbase piece.
 10. The apparatus of claim 9, wherein the lateral exitchannel is positioned between and formed in part by the pair of spacedapart male couplers.
 11. The apparatus of claim 9, wherein the lateralexit channel is positioned substantially perpendicular to thelongitudinal axis of the body of the second base piece when the pair ofmale couplers engage the pair of female couplers.
 12. The apparatus ofclaim 9, wherein the second base piece includes a recess formed betweenthe pair of spaced apart female couplers and configured to engage the atleast one instrument when the pair of male couplers engage the pair offemale couplers to fasten the first and second base pieces together andretain the at least one instrument therebetween.
 13. The apparatus ofclaim 8, wherein the longitudinal axes of the first and second elongatedbodies are parallel to each other upon engagement of the pair of malecouplers with the corresponding pair of female couplers.
 14. Theapparatus of claim 13, wherein a portion of a first side of each of theelongated bodies facing the burr hole contact each other upon engagementof the pair of male couplers with the pair of female couplers.
 15. Theapparatus of claim 6, wherein the hole in the first end of the firstbase piece is disposed on a diagonally opposing side of the burr holefrom the hole in the first end of the second base piece such that thesecond end of each of the first and second base pieces rotates towardthe respective first ends of the first and second base pieces uponrotation of each of the first and second base pieces towards a center ofthe burr hole to a closed position.
 16. The apparatus of claim 10,wherein the lateral exit channel includes first and second spaced apartwalls, each wall having a chamfer at opposed ends thereof to facilitateentry and exit of the at least one instrument.
 17. The apparatus ofclaim 16, wherein the first and second walls of the lateral exit channelextend beyond the first side and an opposite second side of theelongated body of the first base piece.
 18. An apparatus comprising: atwo-piece base including a first base piece and a second base piece, thefirst and second base pieces each including an elongated body portionextending between first and second ends about a longitudinal axis, thefirst end of the first base piece and the first end of the second basepiece including respective holes sized and shaped for receiving afastener therethrough for rotatable motion thereabout, the second end ofthe first base piece including a pair of spaced apart male couplerssized and shaped to engage a corresponding pair of spaced apart femalecouplers disposed on the second end of the second base piece, the firstbase piece including a lateral exit groove formed by the pair of spacedapart male couplers and the respective elongated body and having an axisperpendicular to the longitudinal axis of the elongated body of thefirst base piece, the first base piece being sized and shaped to bedisposed along a first side of a burr hole and the second base piecebeing sized and shaped to be disposed along a second side of the burrhole such that the hole in the first end of the first base piece isdisposed on a diagonally opposing side of the burr hole from the hole inthe first end of the second base piece, wherein the first base piece isspaced apart from the second base piece in an open position and the pairof male couplers of the first base piece are operable to engage thecorresponding pair of female couplers of the second base piece in aclosed position of the base pieces to retain at least one instrumentextending between the first and second base pieces into the burr holesuch that a portion of the retained instrument is received in thelateral exit groove.
 19. The apparatus of claim 18, wherein theelongated body portions of the first and second base pieces each includea first side and an opposite second side, the first and second sidesbeing substantially parallel to the respective longitudinal axes,wherein the first and second base pieces are configured such that therespective first sides are spaced apart from and facing each other inthe open position and contacting each other in the closed position. 20.The apparatus of claim 19, wherein the first and second base piecesrotate within substantially the same plane about parallel spaced apartaxes extending through a center of the respective holes in the first endof the first and second base pieces and perpendicular to thelongitudinal axes of the first and second base pieces.
 21. The apparatusof claim 20, wherein the pair of male couplers and the pair of femalecouplers are each are spaced apart a first distance from the respectiveholes in the first end of the first and second base pieces.
 22. Theapparatus of claim 19, wherein the second base piece includes a recessformed in the first side thereof and between the pair of spaced apartfemale couplers, the recess aligning with the lateral exit channel whenthe pair of male couplers engage the pair of female couplers in theclosed position to fasten the first and second base pieces together toretain the at least one instrument therebetween.